Utilization of activating and masking effects by ligands for highly selective catalytic spectrophotometric determination of copper and iron in natural waters

Environmental remediation processes by zero valence copper: reaction mechanisms

Recent studies have shown Cu(0) as a promising material for the removal of organic and inorganic pollutants. However, there is no review addressing the studies performed. This fact may be related to the toxicity of the particles and the copper released in solution that has not motivated researchers, which entails in a reduced number of publications. However, studies point out how to solve the problem of Cu deposition in support materials. In this work, a detailed review of Cu(0) applications was performed. The specific focus was the reaction mechanisms related to adsorption, oxidation, and reduction processes. Initially, the resources that allow the understanding of the reaction mechanism, such as characterization techniques and the experimental conditions for investigation of the species involved in the process, were presented. The studies were evaluated separately, showing the mechanisms involved only with the application of Cu(0) in pure and isolated form and in association with oxidizing or reductive agents, combined with irradiation sources and ultrasonic waves and in the form supported in polymer matrices. It was verified that by the proposed reaction mechanisms, the exclusive participation of Cu(0), being the removal process, explained only by the redox behavior of copper. Therefore, the review showed the need for future research regarding the redox behavior of the contaminants.

Spectrophotometric determination of Cu(II) in soil and vegetable samples collected from Abraha Atsbeha, Tigray, Ethiopia using heterocyclic thiosemicarbazone

Two selective and sensitive reagents, 2-acetylpyridine thiosemicarbazone (2-APT) and 3-acetylpyridine thiosemicarbazone (3-APT) were used for the spectrophotometric determination of Cu(II). Both reagents gave yellowish Cu(II) complex at a pH range of 8.0-10.0. Beer's law was obeyed for Cu(II)-2-APT and Cu(II)-3-APT in the concentration range of 0.16-1.3 and 0.44-1.05 µg/mL, respectively. The molar absorptivity and of Cu(II)-2-APT and Cu(II)-3-APT were 2.14 × 10(4) at 370 nm, and 6.7 × 10(3) L/mol cm at 350 nm, respectively, while the Sandell's sensitivity were 0.009 and 0.029 µg/cm(2) in that order. The correlation coefficient of the standard curves of Cu(II)-2-APT and Cu(II)-3-APT were 0.999 and 0.998, respectively. The detection limit of the Cu(II)-2-APT and Cu(II)-3-APT methods were 0.053 and 0.147 µg/mL, respectively. The results demonstrated that the procedure is precise (relative standard deviation <2 %, n = 10). The method was tested for Cu(II) determination in soil and vegetable samples. Comparisons of the results with those obtained using a flame atomic absorption spectrophotometer for Cu(II) determination also tested the validity of the method using paired sample t test at the 0.05 level showing a good agreement between them.

Stopped-in-Loop Flow Analysis of Trace Vanadium in Water

The new concept of stopped-in-loop flow analysis (SIL-FA) is proposed, and an SIL-FA method for the catalytic determination of vanadium is demonstrated. In an SIL format, a sample solution merges with reagent(s), and the well-mixed solution is loaded into a loop. The solution in the loop is separated by a six-way switching valve from the main stream. While the reaction proceeds in the stationary loop, the SIL-FA system does not need to establish a baseline continuously. This leads to a reduction in reagent consumption and waste generation compared with traditional flow injection analysis.

Sequential determination of trace amounts of iron and copper in water samples by flow injection analysis with catalytic spectrophotometric detection

A simple flow injection analysis (FIA) method is described for the sequential determination of iron and copper. The detection method for iron and copper is based on their catalytic activities in the oxidation reaction of N,N-dimethyl-p-phenylenediamine (DPD) with hydrogen peroxide. The sequential determination of iron and copper can be carried out by injecting two sample plugs into the FIA system, sequentially. One injection does not contain triethylenetetramine (TETA), and is used for the sum of iron and copper concentration; the other which contains TETA is used only for the iron concentration. For iron determination, TETA is used as a masking agent of copper. The difference in peak height can be used for the calculation of copper concentration. Under the optimal conditions, the detection limits (3sigma) of 0.01 and 0.07 microg L(-1) were obtained for iron and copper, respectively. The proposed method can be applied to the determination of iron and copper in tap water and bottled-drinking mineral water samples. Good recoveries of the method, 98-103% for iron and 98-106% for copper, were achieved.

Simple Bead Injection-Flow Injection System for the Determination of Copper

We demonstrate the extended application of a simple bead injection-flow injection system with a modified simple colorimetric detection unit for the determination of low amount of Cu2+ in samples of different matrices (water and supplement tablet samples) with minimal sample pretreatment by employing ammonium pyrrolidinedithiocarbamate (APDC) reagent.

Successive determination of copper and iron by a flow injection-catalytic photometric method using a serial flow cell

A flow injection-catalytic spectrophotometric method using a serial flow cell was proposed for the successive determination of trace amounts of copper and iron. This method is based on the oxidation coupling of p-anisidine with N,N-dimethylaniline in the presence of hydrogen peroxide to form a dye, which has an absorption maximum at 740 nm. In this indicator reaction, ligands such as 1,10-phenanthroline (phen) and diphosphate were achieved to improve the sensitivity and selectivity. Under the optimal experimental conditions, the determinable ranges were 0.05-5 ppb for copper and 0.5 - 100 ppb for iron, respectively. The RSDs (n = 10) were 0.78% for 0.5 ppb copper(II) and 0.5% for 200 ppb iron(III). The sample throughput was 30 h(-1). The present flow-injection method was applied to the determination of copper and iron in standard river water, tap water, and other natural water samples, and also to the analysis of labile and inert complexes in synthesized samples containing humic acid with copper(II) or iron(III).